Containers made of thermoplastic material, such as PET bottles, are generally made by means of a blowing machine. Linear blowing machines are a commonly used type of blowing machine. After having been manufactured by the linear blowing machine, the containers are transferred to a filling machine, which is commonly of the rotary type, in which the containers are filled with a liquid.
A first problem of the known transfer systems is their complexity and their dimensions.
A further typical problem in a synchronous connection between a linear blowing machine and a rotary filling machine occurs in the frequent case of a difference between the blowing pitch and the filling pitch.
The pitch in a linear blowing machine is the center distance between one blowing cavity and the next cavity in the press, and is defined as a function of the size of the container, attempting to keep it as small as possible compatibly with the structural resistance of the walls of the mold.
The pitch of a rotary filling machine is the distance, along the periphery of a wheel of the filling machine, between a seat of a container to be filled and the next seat. Also in this case, the pitch is defined as a function of the size of the container, but typically it is a multiple of π, e.g. p=(πD)/n, where p is the pitch, n is the number of seats and D is the pitch diameter of the wheel of the filling machine.
In order to avoid this drawback of the difference of pitch between the blowing machine and the filling machine, connection belts are normally used between the two machines apt to create an accumulation of containers which, being no longer constrained to the blowing pitch of the blowing machine, may be loaded into the wheel of the filling machine.
Alternatively to the system for creating accumulations of bottles, a pitch changing system is used in synchronous applications to pass from the blowing pitch to the filling pitch and allow the containers to be loaded into the wheel or star of the filling machine having the same peripheral speed as the wheel of the filling machine in the exchange point. In such applications, the connection between the two machines is typically achieved by means of complex chuck chain systems for conveying the bottles.
However, the known solutions make the overall size of the transfer system disadvantageously too big and the system too complicated.
The need is thus felt for a transfer system which allows to solve the aforesaid problems.